The present invention relates to a sheet of paper, in particular to a sheet of absorbent paper made of creped cellulose cotton and comprising an embossing pattern.
More specifically, the invention concerns a sheet of paper constituted by at least one absorbent paper ply made of creped cellulose cotton and used in the household or in industry, that is being suitable as a rag, a paper towel, etc.
In the field of sanitary or household papers, such as toilet paper or paper towels, it is well known to manufacture sheets of paper composed of several plies of absorbent paper, made, for example, of creped cellulose cotton, also referred to as tissue paper, of a specific surface weight between 12 and 30 g/m2, which are provided with embossed protrusions.
Embossing imparts bulk to the sheet and improves liquid absorption, touch and softness. Attempts have been made to further increase absorptivity by creating multi-layer sheets by combining at least two layers, also called plies, each consisting of at least one embossed sheet.
Two ply embossing and joining modes are currently used depending on the desired properties of the final product.
The first mode is technically known as xe2x80x9cnestingxe2x80x9d. It consists in first embossing the plies separately in order to forms protrusions which are substantially truncated or frusto-pyramidal. Next, an adhesive is deposited on the tops of the protrusions of one of the plies and these plies are configured in such a manner that the sides including the protrusions are opposite one another, the protrusions of one side being situated between the protrusions of the other side. Lastly, the plies are joined in such a manner that glue-coated protrusions nest between the protrusions of the other ply. In this manner, the two are connected by glue spots between the protrusion peaks of one ply and the unembossed zones of the other ply. The structure so attained has voids arrayed to impart improved absorption to the sheet. Moreover, the sheet""s outsides feel smooth and velvety because of the hollows subtended on the back of the protrusions. This technique is described in U.S. Pat. No. 3,867,225.
The second joining procedure is known as tip-to-tip. It differs form the joining mode above by the relative configuration of the two plies. After having been separately embossed, the plies are mounted one on the other so that the tops of the protrusions coincide. The plies are connected to each other by the protrusion tops, tip-to-tip. This technique is illustrated in U.S. Pat. No. 3,414,459.
As regards the practical designs of those structures, whether nested or tip-to-tip, the embossed protrusions mostly are distributed in a pattern whereby the protrusions are aligned in uniform manner in one or more directions. Such a pattern makes possible a mechanically homogenous sheet, but on the other hand its aesthetic appeal is mediocre.
In particular, for the purpose of improving product appearance, applicant has created patterns wherein the protrusions are configured at least in part along certain curves, portions of curves or straight lines, or wherein there are combinations of such portions of curves and/or straight lines. In particular, some of the portions are at least partly mutually parallel. In particular, the protrusions subtend closed curves including circles or arcs of circle that may be concentric.
The objective of the invention is to improve such designs, especially as regards improving appearance.
For that purpose the invention proposes a sheet composed of at least one ply of creped cellulose cotton or tissue paper of a specific surface weight between 12 and 30 g/m2 and having an embossed pattern including a first series of narrow protrusions in the form of embossed tips projecting from one side of the ply and subtending alignments, characterized in that the ply includes a second series of protrusions in association with the first series and in an approximate shape of a low wall, the low wall protrusions projecting from the ply side, and their salient height being less than the height of the protrusions of the first series, each low wall protrusion bridging two adjacent protrusions along the alignments of the first series so as to enhance the visual attraction of the pattern.
In other features of the invention:
the pattern includes at least a first series of protrusions which are aligned along closed-loop designs/geometries and two consecutive protrusions of this first series are interconnected by a small wall-shaped protrusion which is part of the associated second series of protrusions, the designs in particular including at least segments of curves,
the pattern includes several first and second series of protrusions to constitute several concentric closed-loop designs,
the sheet includes several embossing patterns,
when the sheet is an absorbent multi-layer sheet or at least two layers or plies, at least one ply is a sheet of the invention,
each of the external plies includes of a sheet of the invention,
the protrusions project from the inside surface of the external ply,
the multi-layer sheet includes two plies and the associated protrusion series are nested between the associated protrusion series of the other of the two plies.
Furthermore, the invention proposes an engraved cylinder to emboss a sheet of the invention that includes a first series of generally truncated embossing tips which constitute alignments, characterized in that the cylinder includes a second series of embossing protrusions of which the tops"" height is less than that of the embossing tips of the first series, the second series protrusions in particular being thinner than those of the first series.
Lastly, the invention proposes a method for embossing a sheet using a cylinder of the invention and characterized in that the sheets are embossed until they come to rest on the small wall protrusions.
Other features and advantages of the invention are elucidated in the comprehensive description below and in relation to the attached drawings.